Condoleezza Rice is taking her farewell international tour, which this week included a stop at Buckingham Palace to dazzle guests with her piano skills. But for a woman who was once trumpeted as the most powerful in the world and destined for the presidency, her star is rapidly dimming.

In a little over a month, Ms Rice will be slinking back to her old job at California's Stanford University, where an uncertain welcome awaits her.

Thanks to Oliver Stone's movie W, in which she is played by Thandie Newton, her public image has been sealed as a hopelessly ineffectual National Security Adviser. The record shows she was unable to hold back Vice-President Dick Cheney and former Defence Secretary Donald Rumsfeld, and failed miserably in her role as an independent sounding board for George Bush. The foreign policy cognoscenti have determined that Ms Rice was disastrous in her first role in the administration.

David Kay, the former weapons inspector, described her as "probably the worst national security adviser since the office was created". In her second incarnation as Secretary of State, she has been deemed mediocre, at best.

When she last visited the Stanford campus, she got a hostile reception in some quarters. "Rice should not be allowed to return to teaching, she has repeatedly lied," wrote Rachelle Marshall, "campus resident and wife of political science professor emeritus Hubert Marshall", referring to Ms Rice's declarations that the US does not practise torture.

However, in the dog days of George Bush's administration she remains his most loyal aide. Like her boss, she is a workout fanatic who abhors introspection, preferring to work out the stresses of the job with a six-days-a-week cardio routine. At 53, she is single, although she has dated professional football players. And then there is the piano playing at concert level. On Monday night at the Palace, she was accompanied on the violin by Louise Miliband, the wife of the Foreign Secretary.

And despite a somewhat tarnished reputation, now even President Bush has admitted the decision to go to war was based on flawed intelligence, Ms Rice has continued to outshine colleagues. This has largely been through clever PR and by co-operating with authors who wrote three serious biographies of her. Her long journey from the racism of Bull Connor's Alabama is well chronicled and she has steered Mr Bush back from unilateralism and fixed some of the relationships with US allies.

But her legacy may well be that she served as a rubber stamp for a series of disastrous foreign policy decisions. Ms Rice's friends say she hangs on with grim resolve until the facts prove her wrong, at which point she moves on.

Back at Stanford, she will put her students in her shoes. "They are given a problem, some hot spot, and over a week they'd have to be national security adviser solving those problems," Ms Rice told The New York Times. "All of a sudden, it doesn't look so easy."